1. Field of the Invention
This invention relates to an automobile door locking apparatus and more particularly to one including an operating mechanism driven by an electric motor.
2. Description of the Prior Art
An automobile door locking apparatus disclosed in Japanese Published Utility model application No. 54-30317 is shown in FIG. 14. In such an automobile door locking apparatus, it is possible to operate a door latch 91 either manually with a lock knob 93 or electrically with an electric operating mechanism 94. When the locking apparatus is operated by the mechanism, however, the mechanism has the hazard of being accompanied by damage of reduction gears 96 and 97. Namely, if an oscillatory gear 98 is turned downward by a driving motor 95 via the reduction gears 96, 97, then a locking lever 92 is moved downwards via a rod 99. When the locking lever 92 is brought to a lock position and stopped abruptly there, the oscillatory gear 98 is also stopped quickly by the locking lever 92 via the rod 99. This quick stop of the oscillatory gear 98 causes the reduction gears 96, 97 and the motor 95 to stop quickly. These members, however, have a tendency to be turned inertially. Therefore a strong impulsive force is exerted on the teeth of the gears 96, 97 on account of the quick stop of the gears 96, 97 and the motor 95. As a result, some of the teeth are accompanied by a danger of break.
Furthermore, after the door locking apparatus having the above mentioned structure has been electrically operated, the rod 99, to which the oscillatory gear 98, the reduction gears 96, 97 and the motor 5 are connected, is returned to a neutral position by a return spring 100. Accordingly, the above mentioned manual operation of the door latch can be done with a weak force.
However, when the rod 99 begins to be returned by the return spring 100, the oscillatory gear 98, the reduction gears 96, 97 and the motor 95, which are all connected to the rod 99, are at rest. Thus it requires a strong force in effect to start the movement of these members. For this reason, the return spring 100 is required to generate a strong biasing force enough to start the movement.
If the biasing force of the return spring 100 is stronger the load of the motor in the electrical operation becomes so much the heavier. A large electric motor of high power is required as the motor 95.
On the other hand, when the return spring 100 of a large biasing force is operated to return the rod 99 to the neutral position, the oscillatory gear 98 and the reduction gears 97, 98 rotate at a high speed in the returning direction. As a result these gears generate loud meshing noises.